Horse saddles of the English riding type often have protrusions located on the saddle flaps called blocks. These blocks are typically placed either at the front edge of the saddle, the rear edge of the saddle or both the front and rear edges of the saddle. The blocks are either sewn to the leather of the saddle or are attached with Velcro. The purpose of traditional leg blocks is to prevent the rider's leg from moving too far forwards or too far backwards in the saddle.
Saddle blocks are able to be attached to the front and rear area of a saddle flap but are not able to be attached in the center area of the saddle flap because this is where the strap system that secures the saddle to the horse is located. In English saddles the securing strap is called a girth and circles around the midsection of the horse securing on both sides of the saddle by fixed straps called billets. Depending on the saddle type there can be one or multiple billet straps, these straps are confined to the central location of the saddle flap because the horse's shoulders and grooves behind the elbows are used to keep the saddle from sliding forward.
Traditional leg blocks will deform to a degree when the rider's leg is pressed against the block. Traditional blocks are attached to a leather saddle flap, when force is applied to the traditional leg block the flexible leather saddle flap will also deform. Traditional leather saddle flaps and traditional leg blocks are too pliable to create enough resistance to retard the upward momentum of the rider's leg that is created by the motion of the horse.
It is known that shoulder-hip-heel positioning with the shoulder-hip-heel line being located in the area of the girth is appropriate for multiple riding disciplines, however, this can be difficult to achieve without blocks to guide the rider's legs into the appropriate position.
Horse saddles typically have a weight distributing internal component referred to as a saddle tree. Traditionally, saddle trees are comprised of a relatively solid, usually wooden structure which is used to transfer the weight of the rider evenly over the horse's back. Stirrups are affixed to the saddle tree by a stirrup bar which holds the stirrup strap. The stirrup bar allows the stirrup strap to become dislodged, preventing a fallen rider from being dragged behind the horse. The stirrup bar is not placed in the center of the saddle in the shoulder-hip-heel line and girth area because the stirrup bar will interfere with the rider's inner thigh. Also, the central area of the saddle is less reinforced and is more prone to damage from use; this is why traditionally the stirrup bar is affixed to the front portion of the saddle tree. Forward placement of the stirrup bar encourages sub-optimal rider posture. It is known that shoulder-hip-heel positioning is appropriate for multiple riding disciplines, however, this is difficult to achieve with a forward stirrup attachment.
Furthermore, riders typically experience instability in the saddle coincident with movement of the horse. Instability can be experienced on horses with bouncy or exuberant gaits, in jumping activities, during activities that involve high speeds or activities involving changes in the rate of speed. Improvements in saddles that provided riders with increased security in the saddle and diminished the negative impact of the rider's movements on the horse's back would be of great benefit.